Crystal composition (cc) comprising 4,4&#39;-dichlorodiphenylsulfoxide crystals (c)

ABSTRACT

The invention relates to a crystal (C) consisting of at least 95% by weight of 4,4′-dichlorodiphenylsulfoxide, 0 to 2% by weight of impurities and 0 to 3% by weight of an organic solvent (os). Moreover, the present invention relates to a crystal composition (CC) comprising crystals (C) and a process for the production of the crystal composition (CC) and the crystal (C).

The invention relates to a crystal (C) consisting of at least 95% byweight of 4,4′-dichlorodiphenylsulfoxide, 0 to 2% by weight ofimpurities and 0 to 3% by weight of an organic solvent (os). Moreover,the present invention relates to a crystal composition (CC) comprisingcrystals (C) and a process for the production of the crystal composition(CC) and the crystal (C).

4,4′-dichlorodiphenylsulfoxide is also called1-chloro-4-(4-chlorophenyl)sulfinyl benzene orbis(4-chlorophenyl)sulfoxide. 4,4′-dichlorodiphenylsulfoxide is a whiteto pale yellow solid and has a molecular weight of 271.16 g/mol, achemical formula C₁₂—H₈—Cl₂—OS and the CAS-registry-number of4,4′-dichlorodiphenylsulfoxide is 3085-42-5, the chemical structure isas follows

4,4′-dichlorodiphenylsulfoxide is commercially available, for examplefrom abcr GmbH Switzerland, Alfa Aesar or TCI America.

For the production of 4,4′-dichlorodiphenylsulfoxide several processesare known. One common process is a Friedel-Crafts-Reaction with thionylchloride and chlorobenzene as starting materials in the presence of acatalyst, for example aluminum(III)chloride or iron(III)chloride. Sun,X. et al, “Iron(III) chloride (FeCl ₃)-catalyzed electrophilic aromaticsubstitution of chlorobenzene with thionyl chloride (SOCl ₂) and theaccompanying auto-redox in sulfur to give diaryl sulfides (Ar ₂ S):Comparison to catalysis by aluminum chloride (AlCl ₃)”, phosphorus,sulfur, and silicon, 2017, Vol. 192, No. 3, pages 376 to 380, and Sun,X. et al, “Investigations on the Lewis-acids-catalysed electrophilicaromatic substitution reactions of thionyl chloride and selenylchloride, the substituent effects, and the reaction mechanisms”, Journalof Chemical Research 2013, pages 736 to 744, discloses general processesfor the production of 4,4′-dichlorodiphenylsulfoxide. In these documentsthe reaction mixture containing 4,4′-dichlordiphenylsulfoxide is pouredinto ice water. Subsequently diethylether is added and all the contentsare added to a separation funnel and the organic product is extractedwith diethylether. Then all the ether solutions are combined dried withsodium sulfate and filtered. Hereinafter the diethylether is removed toobtain 4,4′-dichlorodiphenylsulfoxide.

U.S. Pat. No. 2,618,582 discloses a process for the preparation ofdiaryldisulfoxides. In example II of U.S. Pat. No. 2,618,582, thepreparation of di-p-(chlorophenyl)disulfoxide is disclosed, which isalso named 4,4′-dichlorodiphenyldisulfoxide. This compound has a meltingpoint of 136° C. and the following chemical structure:

RU 2159764 C1 discloses a process for the preparation of4,4′-dichlorodiphenylsulfoxide. The product is recrystallized fromchloroform. RU 2158257 C1 also discloses a process for the preparationof 4,4′-dichlorodiphenylsulfoxide, wherein the product is recrystallizedfrom ethyl acetate.

Commercially available 4,4′-dichlorodiphenylsulfoxide is provided inparticulate powder form. In the processes described in the abovementioned documents 4,4′-dichlorodiphenylsulfoxide is also obtained inparticulate powder form.

The powdery particulate 4,4′-dichlorodiphenylsulfoxides commerciallyavailable, and the powdery particulate 4,4′-dichlorodiphenylsulfoxidesobtained in the processes described in the above mentioned documents,however, for some applications show insufficient flowability. Moreover,in some cases the content of by-product contained in the4,4′-dichlorodiphenylsulfoxides or the APHA-color number is too high.

Therefore, the object underlying the present invention is to provide4,4′-dichlorodiphenylsulfoxide in particulate form, which does not havethe above-mentioned disadvantages of the prior art or has them only in asignificantly reduced extent.

This object was solved by a crystal composition (CC) comprising crystals(C), wherein the crystals (C) consist of

-   -   (a) at least 95% by weight of 4,4′-dichlorodiphenylsulfoxide,    -   (b) 0 to 2% by weight of impurities and    -   (c) 0 to 3% by weight of an organic solvent (os),        based on the total weight of the crystals (C) contained in the        crystal composition (CC), wherein the crystal composition (CC)        has    -   a d10,₃-value in the range of 100 to 400 μm,    -   a d50,₃-value in the range of 300 to 800 μm and    -   a d90,₃-value in the range of 700 to 1500 μm,        wherein the d10,₃-value is lower than the d50,₃-value and the        d50,₃-value is lower than the d90,₃-value.

It had been found that, surprisingly, the crystal composition (CC) showsa better flowability compared to the particulate4,4′-dichlorodiphenylsulfoxides described in the state of the art.Moreover, it has been found that the crystals (C) comprised in thecrystal composition have a low content of by-product, a low content ofresidual solvent as well as a low APHA-color number.

Crystal Composition (CC)

The crystal composition (CC) comprises crystals (C). In a preferredembodiment the crystal composition (CC) comprises at least 95% by weightof the crystals (C), more preferred the crystal composition (CC)comprises at least 98% by weight of crystals (C) even more preferred thecrystal composition (CC) comprises at least 99% by weight of thecrystals (C) and particularly preferred the crystal composition (CC)comprises at least 99.5% by weight of crystals (C) in each case based onthe total weight of the crystal composition (CC). In an even morepreferred embodiment the crystal composition (CC) consists of thecrystals (C).

Therefore, another object of the present invention is a crystalcomposition (CC), wherein the crystal composition (CC) comprises atleast 95% by weight of crystals (C), based on the total weight of thecrystal composition (CC).

The crystal composition (CC) of the invention generally has:

a d10,₃-value in the range of 100 to 400 μm,

a d50,₃-value in the range of 300 to 800 μm and

a d90,₃-value in the range of 700 to 1500 μm.

Preferably, the crystal composition (CC) of the invention has:

a d10,₃-value in the range of 200 to 400 μm,

a d50,₃-value in the range of 400 to 750 μm and

a d90,₃-value in the range of 800 to 1200 μm.

In each case on condition that the d10,₃-value is lower than thed50,₃-value and the d50,₃-value is lower than the d90,₃-value.

In the context of the present invention the “d10,₃-value”,“d50,₃-value”, and “d90,₃-value” describe the particle sizes based onthe volume of the particles.

In the context of the present invention, the “d10,₃-value” is understoodto mean the particle size at which 10% by volume of the particles,preferably the crystals (C), based on the total volume of the particles,preferably the crystals (C), are smaller than or equal to thed10,₃-value and 90% by volume of the particles, preferably the crystals(C), based on the total volume of the particles, preferably the crystals(C), are larger than the d10,₃-value. By analogy, “d50,₃-value” isunderstood to mean the particle size at which 50% by volume of theparticles, preferably the crystals (C), based on the total volume of theparticles, preferably the crystals (C), are smaller than or equal to thed50,₃-value and 50% by volume of the particles, preferably the crystals(C), based on the total volume of the particles, preferably the crystals(C), are larger than the d50,₃-value. Correspondingly, the “d90,₃-value”is understood to mean the particle size at which 90% by volume of theparticles, preferably the crystals (C), based on the total volume of theparticles, preferably the crystals (C), are smaller than or equal tod90,₃-value and 10% by volume of the particles, preferably the crystals(C), based on the total volume of the particles, preferably the crystals(C), are larger than d90,₃-value.

The particle sizes of the crystals (C) comprised in the crystalcomposition (CC), the d10,₃-values, the d50,₃-values and thed90,₃-values, as well as the average aspect ratios (b/l₃), the averagesphericity (SPTH₃), the average X_(c min) diameter and the averagemaximum Feret diameter (X_(Fe max)) are determined with a Camsizer® XT(of the company Retsch Technology) using the measuring methods describedin the manual “CAMSIZER® Caracteristics, Basics of definition DIN 66141,Retsch Technology dated Nov. 5, 2009” which is available under thefollowing www.-link:http://www.horiba.com/fileadmin/uploads/Scientific/Documents/PSA/Manuals/CAMSIZER_Characteristics_Nov2009.pdf

The particle sizes (hereinafter the wording “particle size” and“particle diameter” are used synonymously and have the same meaning) aredetermined on basis of definition DIN 66141 dated February 1974.Therefore, the crystal composition (CC) is fed via a vibrating feederpast the measurement optic of the Camsizer® XT at room temperature (20°C.) and normal pressure (1,01325 bar), wherein at least 80 000particles, preferably crystals (C), are measured.

The d10,₃-values, the d50,₃-values and the d90,₃-values are determinedby the X_(area) method. With the measuring method X_(area) the particlediameter is calculated by the area of particle projection using thefollowing formula:

${X_{area} = \sqrt{\frac{4A}{\pi}}},$

wherein the diameter of the area equivalent circle with a volume of asphere with the diameter of X_(area) is determined.

The bulk density of the crystal composition (CC) is generally in therange of 600 to 950 kg/m³, preferably in the range of 700 to 850 kg/m³and more preferably in the range of 720 to 820 kg/m³. The bulk densityof the crystal composition (CC) is determined according to EN ISO60:2000-01; DIN 5 3 468.

The tappered density (measured after 1250 lifts) of the crystalcomposition (CC) is generally in the range of 700 to 1050 kg/m³,preferably in the range of 800 to 950 kg/m³ and more preferably in therange of 820 to 920 kg/m³. The tappered density of the crystalcomposition (CC) is determined according to DIN ISO 787 part 11 (after1250 lifts).

The Hausner ratio of the crystal composition (CC) is generally in therange of 1.05 to 1.27, preferably in the range of 1.08 to 1.25 and morepreferably in the range of 1.1 to 1.2.

The Hausner ratio is the ratio of tappered density to bulk density. TheHausner ratio is a parameter for the flowability of particulatecompositions, wherein the flowability is classified according to thefollowing table:

Hausner ratio Flowability 1.05-1.18 Excellent 1.14-1.19 Good 1.22-1.27Acceptable  1.3-1.54 Poor 1.49-1.61 Very Poor >1.67 Not Flowing

Another object of the present invention, therefore, is a crystalcomposition (CC), wherein the Hausner ratio is in the range of 1.05 to1.27.

The crystal composition (CC) preferably has a flowability (ff_(c))according to Jenike and ASTM-D 6773 at an initial shear stress of 3 kPain the range of 7 to 50, preferably in the range of 8 to 40, morepreferably in the range of 8.5 to 20 and particularly preferred in therange of 9 to 15.

According to Jenike the flowability is classified according thefollowing table:

ff_(c) Flowability <1 Not flowing 1< to <2 Very poor 2< to <4 Poor  4<to <10 Good 10< Excellent

The crystals (C) contained in the crystal composition (CC) according tothe invention generally have an average aspect ratio in the range of 0.2to 1, preferably in the range of 0.3 to 0.8, more preferably in therange of 0.4 to 0.7 and particularly preferred in the range of 0.5 to0.65.

The average aspect ratio of the crystals (C) comprised in the crystalcomposition (CC) is determined with a Camsizer® XT using the method b/l₃as described in the above referenced manual on basis of definition DIN66141 dated February 1974. The aspect ratio is calculated by using thefollowing formula:

${b/l_{3}} = \frac{X_{c\mspace{20mu}\min}}{X_{{Fe}\mspace{14mu}\max}}$

X_(c min) is the volume average particle diameter which is the shortestcort of the measured set of maximum corts of the particle projection(the crystal (C) projection).

FIG. 8 shows an example, how X_(c min) is measured. X_(c min) is thevolume average of the shortest cort over all particles (crystals (C)),comprised in the crystal composition (CC).

The maximum feret diameter (X_(Fe max)) is the volume average particlediameter over all particles (crystals (C)), comprised in the crystalcomposition (CC), which is the longest ferret diameter of the measuredset of feret diameter of a particle. The determination of the maximumferet diameter x_(Fe) max is shown by the way of example in FIG. 8.

The crystals (C) contained in the crystal composition (CC) according tothe invention have generally an average sphericity (SPHT₃) in the rangeof 0.75 to 0.85, preferably in the range of 0.76 to 0.82 and morepreferably in the range of 0.77 to 0.81. The sphericity is measuredaccording to ISO 9276-6:2012-1.

Therefore, another object of the present invention is a crystalcomposition (CC), wherein the average sphericity of the crystals (C) isin the range of 0.75 to 0.85.

The crystal composition (CC) has generally an APHA-color number (ASTMD1209) in the range of 10 to 120, preferably in the range of 15 to 100,more preferably in the range of 20 to 80. The APHA-color numbers weremeasured on a Hach Lange LICO 500 instrument; 2.5 g 4,4′-DCDPSO(4,4′-DCDPSO=4,4′dichlorodiphenylsulfoxide) were dissolved in 20 ml NMPand measured against pure NMP (NMP=N-Methyl-2-pyrrolidone).

Crystal (C)

Another object of the present invention is a crystal (C) consisting of

-   -   (a) at least 95% by weight 4,4′-dichlorodiphenylsulfoxide,    -   (b) 0 to 2% by weight of impurities and    -   (c) 0 to 3% by weight of an organic solvent (os),        based in each case on the total weight of the crystal (C),        wherein the outer surface of the crystal (C) comprises    -   i) a six-sided base surface (bsu) and    -   ii) a six-sided top surface (tsu) and    -   iii) six side surfaces (ssu1 to ssu6), joining the corresponding        sides of the six-sided base surface (bsu) and the six-sided top        surface (tsu).

The crystal (C) can differ from the crystals (C) comprised in thecrystal composition (CC). In a preferred embodiment, the crystal (C)does not differ from the crystals (C) comprised in the crystalcomposition (CC). In a preferred embodiment, therefore, the features andpreferences mentioned above in a view of the crystal composition (CC)apply for the crystal (C) accordingly. In another preferred embodiment,therefore, the features and preferences mentioned hereinafter in view ofthe crystal (C) apply for the crystal composition (CC) accordingly.

Another object of the present invention, therefore, is a crystalcomposition (CC) comprising crystals (C), wherein the crystals (C)consist of

-   -   (a) at least 95% by weight of 4,4′-dichlorodiphenylsulfoxide,    -   (b) 0 to 2% by weight of impurities, and    -   (c) 0 to 3% by weight of an organic solvent (os),        based on the total weight of the crystals (C) contained in the        crystal composition (CC), wherein the crystal composition (CC)        has    -   a d10,₃-value in the range of 100 to 400 μm,    -   a d50,₃-value in the range of 300 to 800 μm and    -   a d90,₃-value in the range of 700 to 1500 μm,        wherein the d10,₃-value is lower than the d50,₃-value and the        d50,₃-value is lower than the d90,₃-value, wherein the outer        surface of the crystals (C) comprises    -   i) a six-sided base surface (bsu) and    -   ii) a six-sided top surface (tsu) and    -   iii) six side surfaces (ssu1 to ssu6), joining the corresponding        sides of the six-sided base surface (bsu) and the six-sided top        surface (tsu)

In a preferred embodiment the crystal (C) comprises at least 96% byweight, more preferably at least 97% by weight and most preferably atleast 98% by weight of 4,4′-dichlorodiphenylsulfoxide, based in eachcase on the total weight of the crystal (C).

In a preferred embodiment the crystal (C) comprises from 0 to 1.5% byweight, more preferably from 0 to 1% by weight of impurities, based ineach case on the total weight of the crystal (C).

In a preferred embodiment the crystal (C) comprises from 0 to 2.5% byweight, more preferably from 0 to 2% by weight, most preferably from 0to 1% by weight and particularly preferred from 0 to 0.7% by weight ofan organic solvent (os), based in each case on the total weight of thecrystal (C).

Another object of the present invention is a crystal (C) wherein theimpurities (b) comprise at least 90% by weight, preferably at least 95%by weight, more preferably at least 98% by weight and particularlypreferred at least 99% by weight of one or more compounds selected fromthe group consisting of 2,4′-dichlorodiphenylsulfoxide,3,4′-dichlorodiphenylsulfoxide, 2,2′-dichlorodiphenylsulfoxide,4,4′-dichlorodiphenyl-sulfide, and one or more aluminum compounds, ineach case based on the total weight of the impurities (b) contained inthe crystal (C).

In another particularly preferred embodiment the impurities contained inthe crystal (C) consist of one or more compounds selected from the groupconsisting of 2,4′-dichlorodiphenylsulfoxide,3,4′-dichlorodiphenylsulfoxide, 2,2′-dichlorodiphenyl-sulfoxide,4,4′-dichlorodiphenylsulfide, and one or more aluminum compounds.

The aluminum compounds optionally contained as impurities in the crystal(C) may be one or more compounds selected from the group consisting ofAlCl₃, Al(OH)Cl₂, Al(OH)₂Cl, Al(OH)₃ and AlO(OH).

The aluminum content in the crystal (C) is preferably in the range of 2to 100 ppm by weight, more preferably in the range of 5 to 80 ppm byweight and most preferably in the range of 7 to 60 ppm by weight, ineach case based on the total weight of the crystal (C). The aluminumcontent is determined as described below in the section examples.

Another preferred object of the present invention is a crystal (C)wherein the organic solvent (os) comprises at least 98% by weight ofmonochlorobenzene, based on the total weight of the organic solvent (os)contained in the crystal (C).

Another preferred object of the present invention is a crystalcomposition (CC), wherein the unit cell of the crystals (C) ismonoclinic, space group C 2/m, cell lengths a=16.05 Å±0.05 Å, b=9.82Å±0.05 Å, c=7.21 Å±0.05 Å, cell angles alpha 90°±0.1°, beta 95.7°±0.1°,gamma 90°±0.1°, and a cell volume 1131.5 Å³±1 Å³. In the presentinvention Å means Ångström and equals 0.1 nm.

The geometry of the outer surface of the crystal (C) is similar to aprism with a six-sided base surface and a six-sided top surface, whereinthe jacket surface of the prism comprises six-side surfaces. FIG. 1Ashows the net of a prism with a symmetrical six-sided base surface (bsu)and a symmetrical six-sided top surface (tsu) and six side surfaces(ssu1 to ssu6).

In a preferred embodiment the six-sided base surface (bsu), thesix-sided top surface (tsu) and the six side surfaces (ssu1 to ssu6)account for at least 90% of the outer surface of the crystal (C).Another object of the present invention therefore, is a crystal (C),wherein the six-sided base surface (bsu), the six-sided top surface(tsu) and the six side surfaces (ssu1 to ssu6) account for at least 90%of the outer surface of the crystal (C).

In a preferred embodiment the six-sided base surface (bsu), thesix-sided top surface (tsu) and the six-side surface (ssu1 to ssu6)account for at least 92% of the outer surface of the crystal (C).

The crystal (C) according to the present invention may contain furthersurfaces for example irregularities or intergrowth. Generally thefurther surfaces of the crystal (C) according to the invention accountfor 0 to at most 10%, preferably from 0 to at most 8% of the outersurface of the crystal (C).

Another preferred object of the present invention is a crystal (C),wherein the diameter (db) of the six-sided base surface (bsu) and thediameter (dt) of the six-sided top surface (tsu) are each independentlyin the range of 50 to 1500 μm, preferably in the range of 100 to 1200μm.

Another preferred object of the present invention is a crystal (C),wherein the length (I1) of the first side surface (ssu1), the length(I2) of the second side surface (ssu2), the length (I3) of the thirdside surface (ssu3), the length (I4) of the fourth side surface (ssu4),the length (I5) of the fifth side surface (ssu5) and the length (I6) ofthe sixth side surface (ssu6) are each independently in the range of 100to 3000 μm, preferably in the range of 200 to 2500 μm.

The six-sided top surface (tsu) and the six-sided base surface (bsu) maybe symmetrical or asymmetrical. If the six-sided top surface (tsu) andthe six-sided base surface (bsu) are symmetrical the six sides (tsi1 totsi6) of the six-sided top surface (tsu) as well as the six sides (bsi1to bsi6) of the base surface (bsu) have the same length. In this casethe distance (dt14) between the first corner (ct1) and the fourth corner(ct4) as well as the distance (dt36) between the third corner (ct3) andthe sixth corner (ct6) and the distance (dt25) between the second corner(ct2) and the fifth corner (ct5) of the top surface (tsu) have all thesame length. If the base surface (bsu) is symmetrical, the distances(db14), (db25) and (db36) also have the same length. Therefore, for asymmetrical top surface (tsu) the diameter (dt) equals the distances(dt14), (dt25) and (dt36). For a symmetrical base surface (bsu) thediameter (db) equals the distances (db14), (db25) and (db36).

In case the crystal (C) has an asymmetrical base surface (bsu) and/or anasymmetrical top surface (tsu) the diameter (db) of the six-sided basesurface (bsu) in a preferred embodiment is the average of the distances(db14), (db25) and (db36). The distance (db14) is the shortest distancebetween the first corner (cb1) and the fourth corner (cb4) of thesix-sided base surface (bsu) of the crystal (C). The distance (db25) isthe shortest distance between the second corner (cb2) and the fifthcorner (cb5) and the distance (db36) is the shortest distance betweenthe third corner (cb3) and the sixth corner (cb6) and the diameter (dt)of the six-sided top surface (tsu) in a preferred embodiment is theaverage of the distances (dt14), (dt25) and (dt6). The distance (dt14)is the shortest distance between the first corner (ct1) and the fourthcorner (ct4) of the six-sided top surface (tsu) of the crystal (C). Thedistance (dt25) is the shortest distance between the second corner (ct2)and the fifth corner (ct5) and the distance (dt36) is the shortestdistance between the third corner (ct3) and the sixth corner (ct6), asillustrated by example in FIG. 1B.

The side surfaces (ssu1 to ssu6) independently of each other may haveessentially the form of a square, a rectangle, a rhombus, a kite, aparallelogram, an isosceles trapezium or an irregular quadrilateral. Incase the side surfaces (ssu1 to ssu6) have an asymmetrical form, thelengths (I1 to I6) of the side surfaces (ssu1 to ssu6) are preferablydetermined as follows. As illustrated in FIG. 10 the length (I1) of thefirst side surface (ssu1) is the average of the shortest distance (I11)between the first corner (ct1) of the top surface (tsu) and first corner(bt1) of the base surface (btu) and the shortest distance (I22) betweenthe second corner (ct2) of the top surface (tsu) and the second corner(bt2) of the second corner (bt2) of the base surface (bsu). Accordingly,in this case the length (I2) of the second side surface (ssu2) is theaverage of the shortest distance (I22) between the second corner (ct2)of the top surface (tsu) and the second corner (bt2) of the secondcorner (bt2) of the base surface (bsu) and the shortest distance (I33)between the third corner (ct3) of the top surface (tsu) and third corner(bt3) of the base surface (btu).

The lengths (I3 to I6) are determined accordingly.

The term “have essentially the form of a square, a rectangle, a rhombus,a kite, a parallelogram, an isosceles trapezium or an irregularquadrilateral” according to the present invention may be defined asfollows: “have essentially the form of a square, a rectangle, a rhombus,a kite, a parallelogram, an isosceles trapezium or an irregularquadrilateral” defines that the side surfaces (ss1 to ss6) of thecrystal (C) occupy at least 80%, preferred at least 85%, more preferredat least 90%, and particularly preferred 50% of the interior surface ofa hypothetical best fit of a square, a rectangle, a rhombus, a kite, aparallelogram, an isosceles trapezium or an irregular quadrilateral inwhich the side surfaces (ss1 to ss6) of the crystal (C) fit.

The dimensions of the crystal (C) are preferably measured using lightmicroscopy.

The crystal composition (CC) according to the present invention can beproduced by a process comprising the steps:

-   -   I) cooling a first liquid mixture comprising        4,4′-dichlorodiphenylsulfoxide dissolved in an organic solvent        (os) to obtain a suspension comprising crystallized        4,4′-dichlorodiphenylsulfoxide and the organic solvent (os),    -   II) filtering the suspension obtained in step I) to obtain a        filtrate comprising 4,4′-dichlorodiphenylsulfoxide dissolved in        the organic solvent (os), wherein the filtrate has a lower        concentration of 4,4′-dichlorodiphenylsulfoxide compared to the        first liquid mixture, and a filter residue comprising the        crystallized 4,4′-dichlorodiphenylsulfoxide,    -   III) concentrating the filtrate obtained in step II) to obtain a        second liquid mixture, wherein the second liquid mixture has a        higher concentration of 4,4′-dichlorodiphenylsulfoxide compared        to the filtrate,    -   IV) recycling at least a part of the second liquid mixture        obtained in step III) into step I), and    -   V) drying the filter residue obtained in step II) to obtain the        crystal composition (CC).

In a preferred embodiment the filter residue obtained in step II) iswashed with an organic solvent (os), preferably monochlorobenzene,before drying according to step V). The washing filtrate is preferablyalso recycled to the concentrating step III).

The crystal (C) according to the present invention can be produced by aprocess comprising the step:

-   -   VI) separating a crystal (C) out of the crystal composition (CC)        obtained in step V).

Another object of the present invention, therefore, is a crystalcomposition (CC) obtained by a process comprising the steps:

-   -   I) cooling a first liquid mixture comprising        4,4′-dichlorodiphenylsulfoxide dissolved in an organic solvent        (os) to obtain a suspension comprising crystallized        4,4′-dichlorodiphenylsulfoxide and the organic solvent (os),    -   II) filtering the suspension obtained in step I) to obtain a        filtrate comprising 4,4′-dichlorodiphenylsulfoxide dissolved in        the organic solvent (os), wherein the filtrate has a lower        concentration of 4,4′-dichlorodiphenylsulfoxide compared to the        first liquid mixture, and a filter residue comprising the        crystallized 4,4′-dichlorodiphenylsulfoxide,    -   III) concentrating the filtrate obtained in step II) to obtain a        second liquid mixture, wherein the second liquid mixture has a        higher concentration of 4,4′-dichlorodiphenylsulfoxide compared        to the filtrate,    -   IV) recycling at least a part of the second liquid mixture        obtained in step III) into step I), and    -   V) drying the filter residue obtained in step II) to obtain the        crystal composition (CC).

And yet another object of the present invention is a crystal (C)obtained by a process comprising the step:

The organic solvent (os) used in the first liquid mixture can be anysolvent in which 4,4′-dichlorodiphenylsulfoxide (DCDSPO) is sufficientlysoluble in particular at a temperature suitable for industrial scaleproduction and from which crystallized DCDPSO can be separated in aconvenient manner. Such organic solvent (os) is for examplechlorobenzene, toluene, xylene, mesitylene, methanol or a mixture of twoor more of said solvents. The organic solvent (os) preferably ischlorobenzene, particularly monochlorobenzene.

Optionally for reducing the solubility of DCDPSO in the first liquidmixture and to improve the crystallization, it is possible toadditionally add at least one drowning-out agent, for example at leastone protic solvent like water, an alcohol, and/or an acid, particularlya carboxylic acid, or at least one highly unpolar solvent like a linearand/or cyclic alkane. With respect to ease of workup water, methanol,ethanol, acetic acid and/or formic acid, particularly water and/ormethanol are preferred drowning-out agents.

-   -   VI) separating a crystal (C) out of the crystal composition (CC)        obtained in step V).

The crystal composition (CC) can be used for the production of monomers,polymers and/or pharmaceuticals. If the crystal composition (CC) is usedas a starting product or intermediate for the production of monomers, itis preferably used for the production of 4,4′-dichlordiphenylsulfone.Therefore, the 4,4′-dichlordiphenylsulfoxide is generally reacted withan oxidation agent in order to obtain the 4,4′-dichlordiphenylsulfone.As an oxidation agent, any oxidation agent can be used wherein organicperoxyacid is preferred.

In case the crystal composition (CC) is used as a starting product orintermediate for the production of polymers, it is preferably used forthe production of polyarylene ether sulfone polymers, whereinpolysulfone (PSU), polyethersulfone (PESU) and/or polybiphenylsulfone(PPSU) are particularly preferred.

If the crystal composition (CC) is used for the production of theabove-mentioned preferred polyarylene ether sulfone polymers, it istypically reacted, as mentioned above, with an oxidation agent to obtain4,4′-dichlordiphenylsulfone. The 4,4′-dichlordiphenylsulfone isgenerally subsequently reacted with an aromatic dihydroxymonomer inorder to obtain the above-mentioned polyarylene ether sulfone polymers.

For the production of polysulfone (PSU), the 4,4′-dichlordiphenylsulfoneis generally reacted with bisphenol A (4,4′-(propane-2,2-diyl)diphenol).In order to obtain polyethersulfone (PESU), the4,4′-dichlordiphenylsulfone is generally reacted with4,4′-dihydroxydiphenylsulfone. In order to obtain polybiphenylsulfone(PPSU), the 4,4′-dichlordiphenylsulfone is generally reacted with4,4′-dihydroxybiphenyl.

Another object of the present invention, therefore, is the use of thecrystal composition (CC) as an intermediate for the production of atleast one product selected from the group consisting of monomers,polymers and pharmaceuticals.

The invention is described in more detail by the examples hereinafterwithout being restricted thereto.

EXAMPLES Production of the Crystal Composition (CC)/the Crystal (C)According to the Invention

For the production of 4,4′-dichlorodiphenylsulfoxide (DCDPSO) 5.5 molaluminum chloride and 40 mol monochlorobenzene (MCB) were fed into astirred tank reactor as a first reactor. Subsequently 5 mol thionylchloride were added into the first reactor within 160 minutes. Thereaction in the first reactor was carried out at a temperature of 10° C.The hydrogen chloride produced during the reaction was withdrawn fromthe first reactor. After finishing the addition of thionyl chloride thereaction mixture in the first reactor was heated to 60° C.

After completion of the reaction in the first reactor, the resultingreaction mixture was fed into a stirred tank reactor as a second reactorcontaining 3400 g aqueous hydrochloric acid with a concentration of 11%by weight. The second reactor was heated to a temperature of 90° C. withstirring. After 30 minutes the stirring was stopped and the mixturecontained in the second reactor separated into an aqueous phase and inorganic phase. The aqueous phase was withdrawn.

The organic phase was washed with 3000 g water while stirring at 90° C.After washing, the stirring was stopped and the mixture separated intoan aqueous phase and in organic phase. The aqueous phase was removed.The organic phase was subjected to a distillation.

Monchlorobenzene was distilled from said organic phase until saturationis reached. The distillation was carried out at a temperature of 88 to90° C. at a pressure of 200 mbar (abs). The saturation was monitored viaa turbidity probe.

Subsequently an evaporation cooling crystallization was performed withthe saturated organic phase containing monochlorobenzene and4,4′-dichlorodiphenylsulfoxide obtained in the above describeddistillation (equals cooling step I) of the present invention) until thetemperature reached 20° C. Therefore, the organic phase was refluxed dueto pressure reduction and simultaneously cooled by the condensed liquid.The pressure at the end of the evaporation cooling process is normallyabout 20 mbar (abs). After the evaporation cooling crystallization asuspension was obtained comprising a crystallized4,4′-dichlorodiphenylsulfoxide and monochlorobenzene.

According to step II) of the present invention the suspension obtainedin step I) was filtered to obtain a filtrate comprising4,4′-dichlorodiphenylsulfoxide dissolved in monochlorobenzene and afilter residue comprising the crystallized4,4′-dichlorodiphenylsulfoxide. The filter residue was washed withmonochlorobenzene and subsequently dried at 100° C. and 100 mbar (abs)in order to obtain the crystal composition (CC) (equals step V) of thepresent invention).

According to step III) the washing filtrate and the filtrate obtained instep II) were subjected to a distillation. In the distillationmonochlorobenzene was removed until the amount of combined filtrate andwashing filtrate was reduced to 25% by weight. The distillation wasoperated at 90° C. sump temperature and 200 mbar (abs). The distilledmonochlorobenzene was reused in the next batch as starting material. 80%by weight of the obtained bottom product (equals second liquid mixtureaccording to step III) of the present invention) were recycled into thecrystallization step of the next batch (equals the cooling step I)according to the present invention).

The crystal composition (CC) was obtained in a steady state yield of1232 g per batch which corresponds to a yield of 91.3%.

4,4′-dichlorodiphenylsulfoxide obtained from commercial suppliers:

-   -   abcr-DCDPSO: 4,4′-dichlorodiphenylsulfoxide obtained from abcr        GmbH    -   Alfa-DCDPSO: 4,4′-dichlorodiphenylsulfoxide obtained from        Alfa-Aesar    -   TCI-DCDPSO: 4,4′-dichlorodiphenylsulfoxide obtained from TCI        GmbH    -   Recryst-DCDPSO: 4,4′-dichlorodiphenylsulfoxide recrystallized        from diethylether    -   Recryst-DCDPSO; CHCl₃: 4,4′-dichlorodiphenylsulfoxide        recrystallized from chloroform    -   Recryst-DCDPSO; EA: 4,4′-dichlorodiphenylsulfoxide        recrystallized from ethyl acetate

Analytical Methods

The d10,₃-values, the d50,₃-values and the d90,₃-values are determinedas described above using a Camsizer®XT with a measuring method x_(area).

GC analysis was performed to determine any organic impurity, solvent andthe purity of the 4,4′-dichlorodiphenylsulfoxide. Samples were dilutedin dimethylformamide (DMF) and the internal standard tridecane was addedto quantify the components based on calibration curves. GC analysis wasperformed using a RTx5 Amine column (0.25 μm) from Restek® using thefollowing temperature ramp: holding 50° C. for 2 minutes, heating 15° C.per minute until 250° C. is reached, holding 250° C. for 15 minutes.

APHA numbers were measured (as described above) on a Hach Lange LICO 500instrument; 2.5 g 4,4′- dichlorodiphenylsulfoxide were dissolved in 20mL N-methyl-2-pyrrolidone (NMP) and measured against pure NMP.

Determination of the aluminum content was done by generating a saturatedsolution of 4,4′-dichlorodiphenylsulfoxide in dimethylformamide togenerate a homogeneous solution. Subsequently, a sample of saidsaturated solution was taken and the weight was determined (100 to 200mg +/−0.1 mg). Afterwards, the following decomposition process wasconducted. 8 ml of concentrated sulfuric acid (96% w/w) were added tothe sample and heated to 320° C. Subsequently, 7 ml of a mixed acid(H₂SO₄ 96% w/w; HClO₄ 70% w/w; HNO₃ 65% w/w in a volume ratio 2:1:1)were added and the sample as then heated to 160° C. Thereafter, theexcess acid was evaporated. Subsequently 12 ml of hydrochloric acid (HCl36% w/w) were added and the mixture was heated to reflux to obtain asolution. The exact volume of said solution was determined by backweighting and correction with the density. Thereafter, the aluminumcontent of the solution was measured by inductively coupled opticalplasma emission spectroscopy. (Instrument IPC-OES Agilent 5100; wavelength Al 394, 401 nm; internal standard SC 361.383 nm)

Bulk density and tapered density were determined as described above.

The flowability (ff_(c)) was determined on a Ring Shear Tester RST-XSaccording to Jenike as described in Dr.-Ing. Dietmar Schulze “Theautomatic Ring Shear Tester RST-01.pc”and ASTM-D 6773 at an initialshear stress of 3 kPa.

According to Jenike the flowability is classified according thefollowing table:

ff_(c) Flowability <1 Not flowing 1< to <2 Very poor 2< to <4 Poor  4<to <10 Good 10< Excellent

The melting point was determined by DSC (Differential ScanningCalorimetry) on a Mettler Toledo DSC3 using a heating rate of 2.5 K/min(30 to 410° C.).

The results are shown in the below table.

Tapered bulk den- AI Particle Bulk sity (1250 Haus- Flow- Melting PurityImpurities MCB content size APHA density lifts) ner ability point Color[wt.-%] [wt.-%] [wt.-%] [ppm] [μm] number [kg/m³] [kg/m³] ratio [ttc] [°C.] abcr- yellow 99.1 4,4′-dichlorodi- n.d. 960 d10,₃ = 17 >4000 n.d.n.d. n.d. 6.5 ± 141.1- DCDPSO powder phenylsulfide d50,₃ = 31 0.4 142.50.17 d90,₃ = 62 2,4′-dichlorodi-

TCl- white 99.1 2,4′-dichlorodi- n.d. <60 d10,₃ = 53 472 n.d. n.d. n.d.5.8 ± 141.9- DCDPSO crytals phenylsulfoxide d50,₃ = 491 0.6 143.6 0.20d90,₃ = 1063 Alfa- white 97.4 4,4′-dichlorodi- 0.12 <60 d10,₃ = 46 1420n.d. n.d. n.d. n.d. 140.9- DCDPSO powder phenylsulfide d50,₃ = 328 143.10.26 d903 = 1097 2,4′-dichlorodi- phenylsulfoxide

Recryst- white 99.9 2,4′-dichlorodi- n.d. <50 d10,₃ = 29 68. n.d. n.d.n.d. 6.6 ± 143.3- DCDPSO powder phenylsulfoxide d50,₃ = 55 0.4 144.60.1. d90,₃ = 1415 CC- white 98.8 4,4′-dichlorodi- 0.50 <50 d10,₃ = 23172 763 874 1.13 9.6 ± 141.2- DCDPSO crystals phenylsulfide 0.2 d50,₃ =497 0.4 144.9 according 2,4′-dichlorodi- d90,₃ = 863 to thephenylsulfoxide invention 0.3 Recryst- white n.d. n.d. n.d. n.d. n.d.n.d. n.d. n.d. n.d. n.d 142.8- DCDPSO crystals 144.1 CHCl₃ Recryst-white n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d 141.9- DCDPSOcrystals 143.6 EA

indicates data missing or illegible when filed

FIGURES AND REFERENCE SIGN LIST

FIG. 1A shows the net of a prism with a symmetrical six-sided basesurface bsu and a symmetrical six-sided top surface tsu and six sidesurfaces ssu1 to ssu6

FIG. 1B shows the top view of the top surface tsu of an asymmetricalprism with a six-sided top surface tsu

FIG. 1C shows the first side surface ssu of an asymmetrical six-sidedprism

FIG. 1D shows one embodiment of the geometry of the outer surface of thecrystal C according to the invention

FIG. 2A shows another embodiment of the geometry of the outer surface ofthe crystal C according to the invention

FIG. 2B shows a photo taken with a light microscope of the geometry ofthe outer surface of the crystal C according to the invention withmarked up edges and reference signs

FIG. 3A shows a photo taken with a light microscope of the crystalcomposition CC showing crystals C (500 μm)

FIG. 3B shows a photo taken with a light microscope of the crystalcomposition CC showing crystals C (200 μm)

FIG. 4A shows a photo taken with a light microscope of4,4′-dichlorodiphenylsulfoxide in particulate powder form obtained fromabcr GmbH (500 μm)

FIG. 4B shows a photo taken with a light microscope of4,4′-dichlorodiphenylsulfoxide in particulate powder form obtained fromabcr GmbH (200 μm)

FIG. 5 shows a photo taken with a light microscope of4,4′-dichlorodiphenylsulfoxide in particulate powder form obtained fromAlfa Aesar (500 μm)

FIG. 6A shows a photo taken with a light microscope of4,4′-dichlorodiphenylsulfoxide in particulate powder form obtained fromTCI GmbH (500 μm)

FIG. 6B shows a photo taken with a light microscope of4,4′-dichlorodiphenylsulfoxide in particulate powder form obtained fromTCI GmbH (1 mm)

FIG. 7A shows a photo taken with a light microscope of4,4′-dichlorodiphenylsulfoxide in particulate powder form recrystallizedfrom diethyl ether (500 μm)

FIG. 7B shows a photo taken with a light microscope of4,4′-dichlorodiphenylsulfoxide in particulate powder form recrystallizedform diethylether (200 μm)

FIG. 8A illustrates the measurement of X_(c min)

FIG. 8B illustrates the measurement of X_(Fe max)

FIG. 9A shows a photo taken with a light microscope of4,4′-dichlorodiphenylsulfoxide in particulate powder form recrystallizedfrom chloroform (200 μm)

FIG. 9B shows a photo taken with a light microscope of4,4′-dichlorodiphenylsulfoxide in particulate powder form recrystallizedfrom chloroform (500 μm)

FIG. 10 shows a photo taken with a light microscope of4,4′-dichlorodiphenylsulfoxide in particulate powder form recrystallizedfrom ethyl acetate (500 μm)

-   C crystal-   bsu six-sided base surface of the crystal (C)-   bsi1 first side of the six-sided base surface bsu-   bsi2 second side of the six-sided base surface bsu-   bsi3 third side of the six-sided base surface bsu-   bsi4 fourth side of the six-sided base surface bsu-   bsi5 fifth side of the six-sided base surface bsu-   bsi6 sixth side of the six-sided base surface bsu-   cb1 first corner of the six-sided base surface bsu-   cb2 second corner of the six-sided base surface bsu-   cb3 third corner of the six-sided base surface bsu-   cb4 fourth corner of the six-sided base surface bsu-   cb5 fifth corner of the six-sided base surface bsu-   cb6 sixth corner of the six-sided base surface bsu-   db diameter of the six-sided base surface bsu-   db14 shortest distance between the first corner cb1 and the fourth    corner cb4-   db25 shortest distance between the second corner cb2 and the-   fifth corner cb5-   db36 shortest distance between the third corner cb3 and the sixth    corner cb6-   tsu six-sided top surface of the crystal C-   tsi1 first side of the six-sided top surface tsu-   tsi2 second side of the six-sided top surface tsu-   tsi3 third side of the six-sided top surface tsu-   tsi4 fourth side of the six-sided top surface tsu-   tsi5 fifth side of the six-sided top surface tsu-   tsi6 sixth side of the six-sided top surface tsu-   ct1 first corner of the six-sided top surface tsu-   ct2 second corner of the six-sided top surface tsu-   ct3 third corner of the six-sided top surface tsu-   ct4 fourth corner of the six-sided top surface tsu-   ct5 fifth corner of the six-sided top surface tsu-   ct6 sixth corner of the six-sided top surface tsu-   dt diameter of the six-sided top surface tsu-   dt14 shortest distance between the first corner ct1 and the fourth    corner ct4-   dt25 shortest distance between the second corner ct2 and the fifth    corner ct5-   dt36 shortest distance between the third corner ct3 and the sixth    corner ct6-   ssu1 first side surface of the crystal (C)-   ssu2 second side surface of the crystal (C)-   ssu3 third side surface of the crystal (C)-   ssu4 fourth side surface of the crystal (C)-   ssu5 fifth side surface of the crystal (C)-   ssu6 sixth side surface of the crystal (C)-   I1 length of the first side surface (ssu1)-   I2 length of the second side surface (ssu2)-   I3 length of the third side surface (ssu3)-   I4 length of the fourth side surface (ssu4)-   I5 length of the fifth side surface (ssu5)-   I6 length of the sixth side surface (ssu6)-   I11 shortest distance between the first corner ct1 and the first    corner bt1-   I22 shortest distance between the second corner ct2 and the second    corner bt2-   I33 shortest distance between the third corner ct3 and the third    corner bt3-   I44 shortest distance between the fourth corner ct4 and the fourth    corner bt4-   I55 shortest distance between the fifth corner ct5 and the fifth    corner bt5-   I66 shortest distance between the sixth corner ct6 and the sixth    corner bt6

1. Crystal composition (CC) comprising crystals (C), wherein thecrystals (C) consist of (a) at least 95% by weight of4,4′-dichlorodiphenylsulfoxide, (b) 0 to 2% by weight of impurities, and(c) 0 to 3% by weight of an organic solvent (os), based on the totalweight of the crystals (C) contained in the crystal composition (CC),wherein the crystal composition (CC) has a d10,₃ -value in the range of100 to 400 μm, a d50,₃ -value in the range of 300 to 800 μm and a d90,₃-value in the range of 700 to 1500 μm, wherein the d10,₃-value is lowerthan the d50,₃-value and the d50,₃-value is lower than the d90,₃-value.2. A crystal composition (CC) according to claim 1, wherein the crystalcomposition (CC) comprises at least 95% by weight of crystals (C), basedon the total weight of the crystal composition (CC).
 3. A crystalcomposition (CC) according to claim 1, wherein the crystal composition(CC) shows a bulk density in the range of 600 to 950 kg/m³.
 4. A crystalcomposition (CC) according to claim 1, wherein the average aspect ratioof the crystals (C) are in the range of 0.2 to
 1. 5. A crystalcomposition (CC) according to claim 1, wherein the average sphericity ofthe crystals (C) is in the range of 0.75 to 0.85.
 6. A crystalcomposition (CC) according to claim 1, wherein the Hausner ratio is inthe range of 1.05 to 1.27.
 7. A crystal composition (CC) according toclaim 1, wherein the unit cell of the crystals (C) is monoclinic, spacegroup C 2/m, cell lengths a=16.05 Å±0.05 Å, b=9.82 Å±0.05 Å, c=7.21Å±0.05 Å, cell angles alpha 90°±0.1°, beta 95.7°±0.1°, gamma 90°±0.1°,and a cell volume 1131.5 Å³±1 Å³.
 8. A crystal (C) consisting of (a) atleast 95% by weight 4,4′-dichlorodiphenylsulfoxide, (b) 0 to 2% byweight of impurities, and (c) 0 to 3% by weight of an organic solvent(os), based in each case on the total weight of the crystal (C), whereinthe outer surface of the crystal (C) comprises i) a six-sided basesurface (bsu) and ii) a six-sided top surface (tsu) and iii) six sidesurfaces (ssu1 to ssu6), joining the corresponding sides of thesix-sided base surface (bsu) and the six-sided top surface (tsu).
 9. Acrystal (C) according to claim 8, wherein the six-sided base surface(bsu), the six-sided top surface (tsu) and the six side surfaces (ssu1to ssu6) account for at least 90% of the outer surface of the crystal(C).
 10. A crystal (C) according to claim 8, wherein the diameter (db)of the six-sided base surface (bsu) and the diameter (dt) of thesix-sided top surface (tsu) are each independently in the range of 50 to1500 μm.
 11. A crystal (C) according to claim 8, wherein the length (I1)of the first side surface (ssu1), the length (I2) of the second sidesurface (ssu2), the length (I3) of the third side surface (ssu3), thelength (I4) of the fourth side surface (ssu4), the length (I5) of thefifth side surface (ssu5) and the length (I6) of the sixth side surface(ssu6) are each independently in the range of 100 to 3000 μm.
 12. Acrystal (C) according to claim 8, wherein the ratio of the average ofthe diameter (db) and the diameter (dt) to the average of the length(I1), the length (I2), the length (I3), the length (I4), the length (I5)and the length (I6) is in the range of 0.2 to
 1. 13. Crystal (C)according to claim 8, wherein the impurities (b) comprise at least 90%by weight of one or more compounds selected from the group consisting of2,4′-dichlorodiphenylsulfoxide, 3,4′-dichlorodiphenylsulfoxide,2,2′-dichlorodiphenylsulfoxide, 4,4′-dichlorodiphenylsulfide, and one ormore aluminum compounds based on the total weight of the impurities (b)contained in the crystal (C).
 14. A crystal composition (CC) accordingto claim 1 obtained by a process comprising the steps: I) cooling afirst liquid mixture comprising 4,4′-dichlorodiphenylsulfoxide dissolvedin an organic solvent (os) to obtain a suspension comprisingcrystallized 4,4′-dichlorodiphenylsulfoxide and the organic solvent(os), II) filtering the suspension obtained in step I) to obtain afiltrate comprising 4,4′-dichlorodiphenylsulfoxide dissolved in theorganic solvent (os), wherein the filtrate has a lower concentration of4,4′-dichlorodiphenylsulfoxide compared to the first liquid mixture, anda filter residue comprising the crystallized4,4′-dichlorodiphenylsulfoxide, III) concentrating the filtrate obtainedin step II) to obtain a second liquid mixture, wherein the second liquidmixture has a higher concentration of 4,4′-dichlorodiphenylsulfoxidecompared to the filtrate, IV) recycling at least a part of the secondliquid mixture obtained in step III) into step I), and V) drying thefilter residue obtained in step II) to obtain the crystal composition(CC), wherein the organic solvent is chlorobenzene, toluene, xylene,mesitylene, methanol or a mixture of two or more of said solvents.
 15. Acrystal (C) obtained by the process of claim 14, further comprising thestep: VI) separating a crystal (C) out of the crystal composition (CC)obtained in step V).
 16. Use of the crystal composition (CC) as anintermediate for the production of at least one product selected fromthe group consisting of monomers, polymers and pharmaceuticals.